Atropine: An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.Muscarinic Antagonists: Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.Parasympatholytics: Agents that inhibit the actions of the parasympathetic nervous system. The major group of drugs used therapeutically for this purpose is the MUSCARINIC ANTAGONISTS.Atropine Derivatives: Analogs and derivatives of atropine.Receptors, Muscarinic: One of the two major classes of cholinergic receptors. Muscarinic receptors were originally defined by their preference for MUSCARINE over NICOTINE. There are several subtypes (usually M1, M2, M3....) that are characterized by their cellular actions, pharmacology, and molecular biology.Hexamethonium Compounds: Compounds containing the hexamethylenebis(trimethylammonium) cation. Members of this group frequently act as antihypertensive agents and selective ganglionic blocking agents.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Pralidoxime Compounds: Various salts of a quaternary ammonium oxime that reconstitute inactivated acetylcholinesterase, especially at the neuromuscular junction, and may cause neuromuscular blockade. They are used as antidotes to organophosphorus poisoning as chlorides, iodides, methanesulfonates (mesylates), or other salts.Physostigmine: A cholinesterase inhibitor that is rapidly absorbed through membranes. It can be applied topically to the conjunctiva. It also can cross the blood-brain barrier and is used when central nervous system effects are desired, as in the treatment of severe anticholinergic toxicity.Parasympathomimetics: Drugs that mimic the effects of parasympathetic nervous system activity. Included here are drugs that directly stimulate muscarinic receptors and drugs that potentiate cholinergic activity, usually by slowing the breakdown of acetylcholine (CHOLINESTERASE INHIBITORS). Drugs that stimulate both sympathetic and parasympathetic postganglionic neurons (GANGLIONIC STIMULANTS) are not included here.Parasympathetic Nervous System: The craniosacral division of the autonomic nervous system. The cell bodies of the parasympathetic preganglionic fibers are in brain stem nuclei and in the sacral spinal cord. They synapse in cranial autonomic ganglia or in terminal ganglia near target organs. The parasympathetic nervous system generally acts to conserve resources and restore homeostasis, often with effects reciprocal to the sympathetic nervous system.Vagus Nerve: The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx).Carbachol: A slowly hydrolyzed CHOLINERGIC AGONIST that acts at both MUSCARINIC RECEPTORS and NICOTINIC RECEPTORS.Mydriatics: Agents that dilate the pupil. They may be either sympathomimetics or parasympatholytics.Muscle, Smooth: Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)Pirenzepine: An antimuscarinic agent that inhibits gastric secretion at lower doses than are required to affect gastrointestinal motility, salivary, central nervous system, cardiovascular, ocular, and urinary function. It promotes the healing of duodenal ulcers and due to its cytoprotective action is beneficial in the prevention of duodenal ulcer recurrence. It also potentiates the effect of other antiulcer agents such as CIMETIDINE and RANITIDINE. It is generally well tolerated by patients.Neostigmine: A cholinesterase inhibitor used in the treatment of myasthenia gravis and to reverse the effects of muscle relaxants such as gallamine and tubocurarine. Neostigmine, unlike PHYSOSTIGMINE, does not cross the blood-brain barrier.Autonomic Agents: Agents affecting the function of, or mimicking the actions of, the autonomic nervous system and thereby having an effect on such processes as respiration, circulation, digestion, body temperature regulation, certain endocrine gland secretions, etc.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Organophosphate Poisoning: Poisoning due to exposure to ORGANOPHOSPHORUS COMPOUNDS, such as ORGANOPHOSPHATES; ORGANOTHIOPHOSPHATES; and ORGANOTHIOPHOSPHONATES.Methacholine Compounds: A group of compounds that are derivatives of beta-methylacetylcholine (methacholine).Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Propranolol: A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.Guanethidine: An antihypertensive agent that acts by inhibiting selectively transmission in post-ganglionic adrenergic nerves. It is believed to act mainly by preventing the release of norepinephrine at nerve endings and causes depletion of norepinephrine in peripheral sympathetic nerve terminals as well as in tissues.Glycopyrrolate: A muscarinic antagonist used as an antispasmodic, in some disorders of the gastrointestinal tract, and to reduce salivation with some anesthetics.Vagotomy: The interruption or removal of any part of the vagus (10th cranial) nerve. Vagotomy may be performed for research or for therapeutic purposes.Muscarinic Agonists: Drugs that bind to and activate muscarinic cholinergic receptors (RECEPTORS, MUSCARINIC). Muscarinic agonists are most commonly used when it is desirable to increase smooth muscle tone, especially in the GI tract, urinary bladder and the eye. They may also be used to reduce heart rate.Phentolamine: A nonselective alpha-adrenergic antagonist. It is used in the treatment of hypertension and hypertensive emergencies, pheochromocytoma, vasospasm of RAYNAUD DISEASE and frostbite, clonidine withdrawal syndrome, impotence, and peripheral vascular disease.Heart Rate: The number of times the HEART VENTRICLES contract per unit of time, usually per minute.Cholinesterase Reactivators: Drugs used to reverse the inactivation of cholinesterase caused by organophosphates or sulfonates. They are an important component of therapy in agricultural, industrial, and military poisonings by organophosphates and sulfonates.Cholinesterase Inhibitors: Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.Bethanechol: A slowly hydrolyzing muscarinic agonist with no nicotinic effects. Bethanechol is generally used to increase smooth muscle tone, as in the GI tract following abdominal surgery or in urinary retention in the absence of obstruction. It may cause hypotension, HEART RATE changes, and BRONCHIAL SPASM.Antidotes: Agents counteracting or neutralizing the action of POISONS.Tetrodotoxin: An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.Ileum: The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.Gastrointestinal Motility: The motor activity of the GASTROINTESTINAL TRACT.Cholinergic Fibers: Nerve fibers liberating acetylcholine at the synapse after an impulse.Autonomic Nervous System: The ENTERIC NERVOUS SYSTEM; PARASYMPATHETIC NERVOUS SYSTEM; and SYMPATHETIC NERVOUS SYSTEM taken together. Generally speaking, the autonomic nervous system regulates the internal environment during both peaceful activity and physical or emotional stress. Autonomic activity is controlled and integrated by the CENTRAL NERVOUS SYSTEM, especially the HYPOTHALAMUS and the SOLITARY NUCLEUS, which receive information relayed from VISCERAL AFFERENTS.Bethanechol CompoundsBradycardia: Cardiac arrhythmias that are characterized by excessively slow HEART RATE, usually below 50 beats per minute in human adults. They can be classified broadly into SINOATRIAL NODE dysfunction and ATRIOVENTRICULAR BLOCK.Oxotremorine: A non-hydrolyzed muscarinic agonist used as a research tool.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Salivation: The discharge of saliva from the SALIVARY GLANDS that keeps the mouth tissues moist and aids in digestion.Receptors, Cholinergic: Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology.Preanesthetic Medication: Drugs administered before an anesthetic to decrease a patient's anxiety and control the effects of that anesthetic.Quinuclidinyl Benzilate: A high-affinity muscarinic antagonist commonly used as a tool in animal and tissue studies.Cholinergic Agonists: Drugs that bind to and activate cholinergic receptors.Scopolamine Hydrobromide: An alkaloid from SOLANACEAE, especially DATURA and SCOPOLIA. Scopolamine and its quaternary derivatives act as antimuscarinics like ATROPINE, but may have more central nervous system effects. Among the many uses are as an anesthetic premedication, in URINARY INCONTINENCE, in MOTION SICKNESS, as an antispasmodic, and as a mydriatic and cycloplegic.Cholinergic Agents: Any drug used for its actions on cholinergic systems. Included here are agonists and antagonists, drugs that affect the life cycle of ACETYLCHOLINE, and drugs that affect the survival of cholinergic neurons. The term cholinergic agents is sometimes still used in the narrower sense of MUSCARINIC AGONISTS, although most modern texts discourage that usage.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Cholinergic Antagonists: Drugs that bind to but do not activate CHOLINERGIC RECEPTORS, thereby blocking the actions of ACETYLCHOLINE or cholinergic agonists.Ganglionic Blockers: Agents having as their major action the interruption of neural transmission at nicotinic receptors on postganglionic autonomic neurons. Because their actions are so broad, including blocking of sympathetic and parasympathetic systems, their therapeutic use has been largely supplanted by more specific drugs. They may still be used in the control of blood pressure in patients with acute dissecting aortic aneurysm and for the induction of hypotension in surgery.Muscarine: A toxic alkaloid found in Amanita muscaria (fly fungus) and other fungi of the Inocybe species. It is the first parasympathomimetic substance ever studied and causes profound parasympathetic activation that may end in convulsions and death. The specific antidote is atropine.Dichlorvos: An organophosphorus insecticide that inhibits ACETYLCHOLINESTERASE.Tropanes: N-methyl-8-azabicyclo[3.2.1]octanes best known for the ones found in PLANTS.Sympatholytics: Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the ADRENERGIC ANTAGONISTS and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see ADRENERGIC AGENTS). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see ADRENERGIC ALPHA-AGONISTS) are included here.Histamine: An amine derived by enzymatic decarboxylation of HISTIDINE. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter.Stomach: An organ of digestion situated in the left upper quadrant of the abdomen between the termination of the ESOPHAGUS and the beginning of the DUODENUM.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Pentolinium Tartrate: A nicotinic antagonist that has been used as a ganglionic blocking agent in hypertension.Muscle Relaxation: That phase of a muscle twitch during which a muscle returns to a resting position.Soman: An organophosphorus compound that inhibits cholinesterase. It causes seizures and has been used as a chemical warfare agent.Bretylium CompoundsMecamylamine: A nicotinic antagonist that is well absorbed from the gastrointestinal tract and crosses the blood-brain barrier. Mecamylamine has been used as a ganglionic blocker in treating hypertension, but, like most ganglionic blockers, is more often used now as a research tool.Depression, Chemical: The decrease in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.Urinary Bladder: A musculomembranous sac along the URINARY TRACT. URINE flows from the KIDNEYS into the bladder via the ureters (URETER), and is held there until URINATION.Trachea: The cartilaginous and membranous tube descending from the larynx and branching into the right and left main bronchi.Receptor, Muscarinic M3: A subclass of muscarinic receptor that mediates cholinergic-induced contraction in a variety of SMOOTH MUSCLES.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.Vasoactive Intestinal Peptide: A highly basic, 28 amino acid neuropeptide released from intestinal mucosa. It has a wide range of biological actions affecting the cardiovascular, gastrointestinal, and respiratory systems and is neuroprotective. It binds special receptors (RECEPTORS, VASOACTIVE INTESTINAL PEPTIDE).Methysergide: An ergot derivative that is a congener of LYSERGIC ACID DIETHYLAMIDE. It antagonizes the effects of serotonin in blood vessels and gastrointestinal smooth muscle, but has few of the properties of other ergot alkaloids. Methysergide is used prophylactically in migraine and other vascular headaches and to antagonize serotonin in the carcinoid syndrome.Gastric Juice: The liquid secretion of the stomach mucosa consisting of hydrochloric acid (GASTRIC ACID); PEPSINOGENS; INTRINSIC FACTOR; GASTRIN; MUCUS; and the bicarbonate ion (BICARBONATES). (From Best & Taylor's Physiological Basis of Medical Practice, 12th ed, p651)Secretory Rate: The amount of a substance secreted by cells or by a specific organ or organism over a given period of time; usually applies to those substances which are formed by glandular tissues and are released by them into biological fluids, e.g., secretory rate of corticosteroids by the adrenal cortex, secretory rate of gastric acid by the gastric mucosa.Metiamide: A histamine H2 receptor antagonist that is used as an anti-ulcer agent.Dimethylphenylpiperazinium Iodide: A selective nicotinic cholinergic agonist used as a research tool. DMPP activates nicotinic receptors in autonomic ganglia but has little effect at the neuromuscular junction.Ophthalmic Solutions: Sterile solutions that are intended for instillation into the eye. It does not include solutions for cleaning eyeglasses or CONTACT LENS SOLUTIONS.Substance P: An eleven-amino acid neurotransmitter that appears in both the central and peripheral nervous systems. It is involved in transmission of PAIN, causes rapid contractions of the gastrointestinal smooth muscle, and modulates inflammatory and immune responses.Reflex: An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.Phenoxybenzamine: An alpha-adrenergic antagonist with long duration of action. It has been used to treat hypertension and as a peripheral vasodilator.Receptor, Muscarinic M2: A specific subtype of muscarinic receptor found in the lower BRAIN, the HEART and in SMOOTH MUSCLE-containing organs. Although present in smooth muscle the M2 muscarinic receptor appears not to be involved in contractile responses.Sympathomimetics: Drugs that mimic the effects of stimulating postganglionic adrenergic sympathetic nerves. Included here are drugs that directly stimulate adrenergic receptors and drugs that act indirectly by provoking the release of adrenergic transmitters.Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Pilocarpine: A slowly hydrolyzed muscarinic agonist with no nicotinic effects. Pilocarpine is used as a miotic and in the treatment of glaucoma.Gastric Fundus: The superior portion of the body of the stomach above the level of the cardiac notch.N-Methylscopolamine: A muscarinic antagonist used to study binding characteristics of muscarinic cholinergic receptors.Tachykinins: A family of biologically active peptides sharing a common conserved C-terminal sequence, -Phe-X-Gly-Leu-Met-NH2, where X is either an aromatic or a branched aliphatic amino acid. Members of this family have been found in mammals, amphibians, and mollusks. Tachykinins have diverse pharmacological actions in the central nervous system and the cardiovascular, genitourinary, respiratory, and gastrointestinal systems, as well as in glandular tissues. This diversity of activity is due to the existence of three or more subtypes of tachykinin receptors.Metipranolol: A beta-adrenergic antagonist effective for both beta-1 and beta-2 receptors. It is used as an antiarrhythmic, antihypertensive, and antiglaucoma agent.Adjuvants, Anesthesia: Agents that are administered in association with anesthetics to increase effectiveness, improve delivery, or decrease required dosage.Receptor, Muscarinic M1: A specific subtype of muscarinic receptor that has a high affinity for the drug PIRENZEPINE. It is found in the peripheral GANGLIA where it signals a variety of physiological functions such as GASTRIC ACID secretion and BRONCHOCONSTRICTION. This subtype of muscarinic receptor is also found in neuronal tissues including the CEREBRAL CORTEX and HIPPOCAMPUS where it mediates the process of MEMORY and LEARNING.Sympathetic Nervous System: The thoracolumbar division of the autonomic nervous system. Sympathetic preganglionic fibers originate in neurons of the intermediolateral column of the spinal cord and project to the paravertebral and prevertebral ganglia, which in turn project to target organs. The sympathetic nervous system mediates the body's response to stressful situations, i.e., the fight or flight reactions. It often acts reciprocally to the parasympathetic system.Splanchnic Nerves: The major nerves supplying sympathetic innervation to the abdomen. The greater, lesser, and lowest (or smallest) splanchnic nerves are formed by preganglionic fibers from the spinal cord which pass through the paravertebral ganglia and then to the celiac ganglia and plexuses. The lumbar splanchnic nerves carry fibers which pass through the lumbar paravertebral ganglia to the mesenteric and hypogastric ganglia.Solanaceous Alkaloids: Alkaloids, mainly tropanes, elaborated by plants of the family Solanaceae, including Atropa, Hyoscyamus, Mandragora, Nicotiana, Solanum, etc. Some act as cholinergic antagonists; most are very toxic; many are used medicinally.BenzilatesParotid Gland: The largest of the three pairs of SALIVARY GLANDS. They lie on the sides of the FACE immediately below and in front of the EAR.Dicyclomine: A muscarinic antagonist used as an antispasmodic and in urinary incontinence. It has little effect on glandular secretion or the cardiovascular system. It does have some local anesthetic properties and is used in gastrointestinal, biliary, and urinary tract spasms.